-LRB- CNN -RRB- -- Bringing a growing health concern to Congress , scientists squared off Thursday over whether cell phones contribute to brain cancer .

Rep. Denis Kucinich of Ohio holds a model of a 5-year-old child 's brain absorbing cell phone radiation .

Studies have indicated that long-term cell phone use may be associated with brain cancer , according to Dr. Ronald Herberman , director of the University of Pittsburgh Cancer Institute , and Dr. David Carpenter , director of Institute for Health and the Environment at University of Albany . They both testified in front of the House Subcommittee on Domestic Policy .

`` I can not tell this committee that cell phones are definitely dangerous . But , I certainly can not tell you that they are safe , '' Herberman said .

Herberman and Carpenter cited the results from a study recently presented by Dr. Lennart Hardell of Örebro University in Sweden .

The results indicated that people who use cell phones have double the chance of developing malignant brain tumors and acoustic neuromas , which are tumors on the hearing nerve . The study also said people under age 20 were more than five times as likely to develop brain cancer .

But Dr. Robert Hoover , director or Epidemiology and Biostatistics Program at the National Cancer Institute , said the study has not yet appeared in a peer-reviewed journal , so has not come under sufficient scrutiny . The evidence for the connection between cell phones and cancer is inconclusive and more research is needed , he said .

`` Larger studies are needed to sort out chance and bias , '' Hoover testified .

Interphone , a series of multinational studies on the risk of cancer from cell phones , has not found an increase in tumors associated with the first 10 years of mobile phone use , he said .

Some findings show an increased risk of tumors diagnosed on the side of the head that the cell phone is pressed against , but this pattern has not been seen consistently , Hoover said .

CTIA , the International Association for Wireless Telecommunications , declined the invitation to testify , Rep. Dennis Kucinich , a former Democratic presidential candidate from Ohio , who led the hearing , said .

Steve Largent , CEO of CTIA , issued a statement Wednesday saying the industry has supported scientific research on these issues and supports the Federal Communications Commision 's safety guidelines .

`` The available scientific evidence and expert reviews from leading global health organizations such as the American Cancer Society , National Cancer Institute , United States Food and Drug Administration and the World Health Organization reflect a consensus based on published scientific research showing that there is no reason for concern , '' Largent 's statement said .

The overall evidence for the cancer-phone link has not been statistically significant at a 95 percent confidence level , a standard in science , Carpenter said . But he also noted that U.S.-funded research is very scarce .

`` Are we at the same place we were with smoking and lung cancer 30 years ago ? '' he asked .

Carpenter and Herberman testified that the risk of brain cancer for children is far greater than for adults . Herberman demonstrated a model showing that the radiation from cell phones would penetrate far deeper into a 5-year-old 's brain than an adult 's . See models from researchers at the University of Pittsburgh ''

But the incidence of brain cancer in children has not increased significantly from the late 1980s to 2005 , Hoover said .

The Federal Communications Commission limits cell phone radio frequency energy emissions , called the specific absorption rate -LRB- SAR -RRB- , at 1.6 watts per kilogram , as measured over one gram of tissue .

The standard was developed in 1997 in consultation with Institute of Electrical and Electronics Engineers , a professional association open to everyone , including manufacturers and health specialists .

But the SAR standard reflects a biological response to cell phone radio frequency energy heating tissue , Kucinich said .

Many experiments show that radio frequency energy does cause `` biological effects '' without heating tissue , although not all of those effects are harmful , Carpenter said . Hoover agreed that there could be such effects related to cancer risk , but they have not been properly vetted in a laboratory .

The FCC itself does not have the expertise to evaluate whether this standard is appropriate protection for possible heath risks , Julius Knapp , director of the FCC 's Office of Engineering and Technology , testified .

The hearing took place just a week after the Cleveland Clinic reported a study showing that keeping a cell phone on talk mode in a pocket can decrease sperm quality .

Herberman had issued a warning to physicians , scientists , and staff at the University of Pittsburgh in July advising them to limit cell phone use because of the possible risk of cancer . The Israeli Health Ministry endorsed this recommendation within a week , he said .

Ellen Marks of Lafayette , California , whose husband found out he had a brain tumor on his right frontal lobe in May , attended the hearing .

The tumor is on the same side of his head where he held his cell phone , which he used about 30 hours per month . She believes the tumor is the result of cell phone use .

`` I often threatened to throw it in the garbage , and how I wish I had , '' she said . `` This horror could have been avoided with a simple warning . ''

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Studies conflict ; do not consistently show cell phones cause cancer , expert says

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Expert says he can not say they are definitely dangerous or definitely safe

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Children are at higher risk for cancer-causing radiation from phone , scientist says

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Woman at House panel hearing says her husband 's brain cancer from cell phone